In the Dreamtime an Ancestral Being called Yingana came from Macassar across the sea to the shores of Western Arnhem Land, bearing in her body many strange creatures, half human, half/animal, bird, fish or reptile, which she deposited at various places as she wandered over the country. She had the ability, as had all Ancestral Beings, to change shape at will, and this was usually into that of a Rainbow Serpent, so that she could travel long distances either underground or concealed by grass and bushes.
Yingana also brought with her a large dilly bag filled with yams and a long digging stick with which to plant them and later dig them up.. Since then yams have been one of the most important sources of food.
Yingana eventually grew dissatisfied with the strange shapes living around her, and swallowed every living creature, regurgitating them in their present day forms of individual species. Then she grew two eggs in her belly and gave birth to a son called Ngalyod and a daughter called Ngalkunburriyaymi. Of these the most important was Ngalyod, who often travelled with his mother as she went throughout Western Arnhem Land and Croker Island, creating sacred sites such as rocks, hills, plants and trees, which altered forever the shape of the landscape. His sister also had the power to create sacred sites, but she confined her activities to local areas around her home, a waterlily-covered billabong near Nimbuwah Rock, about 50 kilometres from Oenpelli.
Ngalyod is also the controller of the seasons of the Wet and the Dry, and in sacred ceremonies he is honoured in song and dance cycles in order to keep him happy. If he becomes angry for any reason he can create heavy clouds with the vapour from his breath, then flick out his tongue to cause zigzag lightning before thrusting his fangs into the clouds and bringing down torrential rain.
As floods cover the earth, Ngalyod finds it easy to slide up to his victim and swallow him. Both Yingana and her daughter had the bodies of snakes and the tails of fish, whereas Ngalyod had the tail of a serpent but could assume at will the face and body of a crocodile or a kangaroo instead of a serpent's head.
In secret and sacred ceremonies the deeds of Yingana are related in a series of song and dance cycles. Her dilly bag and digging stick are regarded as very sacred objects, and a large, closely woven and highly decorated dilly bag is carried by an important ritual leader who tells how it was brought to Arnhem Land.